Detailed mechanism of the ligand-to-metal energy transfer of silica-coated Tb(III) complex with p-sulfonatothiacalix[4]arene

The energy transfer mechanism, which provides the feeding of the excited D-5(4) level of Tb(III), has been studied by photoluminescence spectroscopy in the Tb(III) complex with p-sulfonato-thiacalix[4]arene doped into the silica nanoparticles. The quantitative evaluation of the rate constants of each energy transfer step highlights two channels of the energy transfer from the singlet ligand-centered level to the D-5(4) level. The channel one occurs via the triplet ligand level S-1 -> T-1 -> D-5(4), the second channel comes about via the higher levels of Tb(III) S-1 -> D-5(3)-> D-5(4). The latter channel determines the rate of the luminescence decay of the D-5(4) level. The high luminescence efficiency and enhanced thermo- and photo-stabilities make the Tb(III) complexes doped into the silica nanoparticles a promising nanomaterial for medical and bioanalytical applications. (C) 2014 Elsevier B.V. All rights reserved.